A variable capacity store for elongated articles where an endless conveyor is subdivided into an active path and a passive path is previously known from EP 738478. EP 738478 discloses a variable-capacity store for elongated articles. The store comprises an input station and an output station located in series along a path along which elongated articles are fed. The articles are fed by a single endless conveyor, which is subdivided into an active path and a passive path. The active path extends from the input station to the output station and the passive path extends from the output station to the input station. The active path is formed by a part of the endless conveyer, which is wound around a first set of drums in a first spiral. The passive path, or return branch, is formed by a part of the endless conveyor, which is wound around a second set of drums in a second spiral.
A drawback of the variable capacity store of the above type is that the transfer between the active path and passive path is performed at a single point, which is where the endless conveyer leaves the first spiral to enter the second spiral or vice versa, in dependence of whether the active path should be lengthened or shortened. The friction between the drums and the endless conveyor will increase as the number of turns increases from the point of entrance where the active and passive paths are connected. This implies that, when trying to change the division between the active path and passive path, by removing part of the active path from the passive path or by introducing part of the passive path into the active path, the tension of the chain will increase from the point of entrance where the active and passive paths are connected as the number of turns increases. When a reservoir is used in a process which has relatively large short term variations in the capacity of a delivering device, which is arranged to feed the reservoir, and a receiving device, which is arranged to be fed by the reservoir, it is of importance that the capacity of the reservoir can be altered quickly. A limiting factor in this regard, is that the endless conveyor is designed to support a maximum tension. The tension in the endless conveyor is dependent on the velocity of the change of length of the active and passive path. Since the tension in the endless conveyor increases as the number or turns increases, the maximum feed in-feed or feed out velocity from the active path will be determined from the tension in the chain at the last turn, calculated from the point of entrance. For a conveyor of a determined rigidity, there will be a maximum number of turns allowed for a specific maximum feed in-feed or feed out velocity from the active path. If the designer would need more turns in order to create a larger variable capacity store, the designer would have to contemplate to make a more rigid conveyor, which in turn would increase the weight of the chain and thus require a complete redesign of the store.